Hi. I use cornstarch (cornflour in the U.K.) in my cookies. I bake mine slowly to make them crunchy rather than chewy though. I like the finer texture the cornstarch gives, though I’m considering using a little less as I think they can be a bit too dry once they have the dry icing on as well. Currently I use 100g cornstarch and 375g plain flour. I don’t use any type of raising agent.